Pressing punch and die



Jan. 15, 1957 w. s. BANZHF, JR 2,777,162

PREssING PUNCH AND DIE 2 Sheets-Sheet l Filed Oct. 29. 1952 /A/l/E/vrop W 5. BANZHOEJH.

A7' TORNEV Jan. 15, 1957 w. s. BANZHOF, JR 2,777,162

PREssING PUNCH AND DIE 2 Sheets-Sheet 2 `c'iled Oct. 29, 1952 FIG 4 4 E a f@ w 5M mn Fm M mfg 4 O H 11m HMH l MDW MoU, 0U mp PTM l www U m @Mmm ATTORNEY PRESSlNG PUNCH AND DIE William S. Banzhof, Jr., Morris Plains, N. J., assigner to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application October 29, 1952, Serial No. 317,491

3 Claims. (Cl. lil-16.5)

This invention relates to forming presses and particularly to punch and die structures used in the manufacture of wafer-like articles.

One article of this type used in communication equipment is a resistor which Varies in resistance with the magnitude of the current through it and is commonly rei ferred to as a varistor. The present invention has to do with the forming of varistors in ilanged disc form from powdered material such as silicon carbide. These discs must be formed to very close dimensional limits, particularly with respect to thickness. lt is therefore necessary that the punches and dies used in forming such discs be accurately maintained and this presents ay diilicult problem because the powdered material, being extremely abrasive, subjects the punches and dies to rapid wear.

The object; of the present invention is a punch and die structure for use in apress and in which the punches and dies may be readily and accurately maintained.

With this and other objects in view the invention comprises a punch and d ie structure in which upper and lower punches, cooperating with a die, are faced with rubber which resists abrasion and produces a desirably rough surface on the finished disc and are provided with retracted sleeves for forming the flange. Since the end faces of the sleeves are subject to rapid wear they are adjustably mounted on the punches so that the faces may be reground as required and reset to their original relation with respect to the punch faces. The die is preferably fitted with an insert of very hard material such as tungsten carbide, press fitted or otherwise mounted in the body of the die to permit regrinding and adjustment of its position in the die.

According to a further feature the die or'the upper face of the insert, when used, is chainfered to provide space for measuring the excess material required to form the flange, the angle of chamfering being such that the eXGeSS material flows into the die cavity when the lower punch is withdrawn from the measuring position.

i Other objects and advantages will be apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:

Fig. l is a vertical sectional view of a portion of a press illustrating one set of punches and die of the apparatus;

Fig. 2 is a fragmentary vertical sectional view illustrating the positions of the punches relative to the die during the measuring step of the operating cycle;

Fig. 3 is a fragmentary vertical sectional view illustrating the relative positions of the punches and die during the forming of the operation;

Fig. 4 is a fragmentary vertical sectional view illustrating the relative positions of the punches and die during the ejecting step of the operation;

Fig. 5 is a chart illustrating the relative positions of the forming ends of the punches with respect to the top of the die during the operating cycle of the press, and

Fig. 6 is an enlarged isometric view of an article produced by the apparatus.

nite States Patent O uring position indicated at Alti in Fig. 5.

2,777,162 Patented Jan. 15, 1957 Referring now to the drawings, attention is iirst directedl to Fig. l which illustrates portions of a press selected to illustrate the invention. Although a plurality of sets of punches and dies as illustrated in Fig. 1 of the drawings are employed in high speed rotary tablet presses, the disclosure of one set in a single press illustrates the present invention. The press selected includes a table or die holder 10 interposed between an upper punch holder 11 and a lower punch holder 12. The punch holders are reciprocated in a given order relative to each other and the table to produce an operating cycle as will be described in connection with Fig. 5 hereinafter.

The table 10 is apertured at 14 to receive a die indicated generally at 15 which includes a main member or body 16 centrally apertured to receive a sleeve 17. The body or main member 16 may be formed of any suitable material softer and less expensive than is required for the cavity of the die which is embodied in the` sleeve 17. The sleeve 17 has its upper end chamfered at 18 to receive excess material as hereinafter described. The sleeve 17 in the present embodiment of the invention is press lit in the aperture of the main member 16 so that, when the sleeve becomes worn, it may be forced outwardly a given distance where it will be ground and re-chamfered for further use.

An upper punch 20 supported at 21 in the upper punch holder 11 has a main or central member 22 threaded at 2,3. An outer member of the upper punch is internally threaded at 26 for engagement with the threaded portion 23, a lock-nut 27 assistingin locking the member 25 in any desired position relative to `the member 22. The lower portion of the member 25 is reduced to produce a tubular portion 28 of a cross-sectional contour corresponding to the contour of the die cavity and eX- tending a given distance beyond the lower end of the central member 22. A replaceable flexible member or rubber disc A29 is positioned adjacent the lower end of the member 22 and is sufficiently larger than the member 22 to lie flat against the said lower end and create a friction-tit in the outer end of the tubular portion 28.

f A lower punch 30 with the exception of its greater length is substantially identical in structure to the upper punch including a main member 32. The main or central member 32 is mounted at 31 in the lower punch holder 12 and includes a threaded portion 33 upon which is mounted an outer member 35, having internal threads similar to the threads 26 of the upper punch. A lock-nut 37 disposed on the threaded portion 33 cooperates with the outer member to lock it in an adjusted position relative to the main member 32. The eXtra length of the lower punch is embodied in the plain portion of the central member 32 and a reduced tubular portion 38, of the outer member 35, vwhich is of a cross-sectional contour similar to that of the die cavity. A replaceable flexible member or rubber disc 39, identical with the rubber disc 29 is disposed in the upper end of the tubular portion 38 resting on and parallel with the upper end of the main member 32.

The operation of the press with the punches and die may be understood more clearly by considering Figs. 2 to 5 inclusive, in connection with Fig. l. Fig. 2, for example. illustrates the upper punch 20 in its raised position away from the die 15 while the lower punch is located at a meas- Fig. 2 illustrates the lower punch cooperating with the die in forming a measuring cup for a given quantity of material when filled to the upper plane of the die. Attention is directed to the chamfered end of the die and the additional quantity of material placed in the die cavity as a result of this chamfered or enlarged die portion. By observing the cycle of operation in Fig. 5, it will be noted that the top of the lower punch moves downwardly to its operating position 41 in advance of the upper punch rso that the material may move uniformly downwardly in the die cavity, evenly distributed upon the upper portion of the punch except adjacent the cavity wall where, itfwill be noted, an extra quantity has been deposited in the annular cavity formed by periphery of the rubber disc 39 and the upper end of the tubular portion 38. Furthermore, the annular formation of the extra quantity of material above the main body of material resulting from the space provided by the ohamfer 1S is distributed so as to ll the cavity produced by the exposed periphery of the rubber disc 29 and the lower end of the tubular portion 28 of the upper punch. When the punches complete the forming operation in the die through necessary motions and pressures applied to the punch holders, an article illustrated in Fig. 6 will be produced. The article indicated generally -at 42, having an annular llange-like outer portion 43 and a reduced or thinner central portion 44, may be exaggerated for the purpose of clarity, but the central portion, as a result of the rubber discs 29 and 39 is rough while the 4annular flanges are provided with smooth surfaces. In this manner, the desired electrical characteristics of the article are produced and central portion 44 will be more readily adaptable for the reception and adherence of metal coatings subsequently applied thereto.

The latter portion of the oper-ating cycle, in the present embodiment of the invention as illustrated in Fig. 4 and at 45 in Fig. 5, includes the return of the upper punch to its upper position away from the Idie followed by raising the Working end of the lower punch out of the die for the ejection of the finished arti-cle, after which the lower punch may be returned to its measuring position 40 as shown in Figs. Zand 5.

It will be apparent that if the ordinary single part punches and dies were employed in the manufacture of articles of highly abrasive materials such as silicon carbide, the eicientilives of these punches and dies would be short, and more important, they could not be reconditioned forfurhter use. It is not only important that the punches and dies be adaptable for several reconditioning operations but that they may be readily adjusted to compensate for such operations and to assure the production of parts which must be held within tine limits.

It is to be understood that the above described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. In a punch press, a die circular in cross-section, a punch having a central member, circular in cross-section and having a flexible material engaging end, an outer member of the punch having a cylindrical portion with a material engaging end adapted to enter the die with the central portion, andmeans to mount the outer member for adjustment on the central member to compensate for wear on the material engaging ends.

2. In a punch press, a die circular in `cross-section, a punch having a central member circular in cross-section and having a working end to enter the die, a tlexible, material engaging member replaceably mounted on the Working end of the central member, an outer member of the punch having a cylindrical portion with a material engaging end adapted to enter the die with the central portion and surround a portion of the flexible member, and means to mount the outer member for adjustment on the central member to compensate for wear on the material engaging end of the outer member.

3. In a punch press having a fixed position die, to receive powdered material, circular in cross-section, open at both top and bottom ends and having an outwardly tapered upper end to receive an extra amount of the material, upper and lower punches for` the die, similar in structure and having central members circular in crosssection with working ends to enter the top and bottom ends respectively of the die, a ilexible, material engaging member replaceably mounted on the working end of each central member, an outer member for each central member of the punches having -a cylindrical portion with a material engaging end surrounding a portion of its respective flexible member and terminating short of the material engaging surface thereof to form 'an annular pocket, means to mount the outer members of the punches for adjustment on their respective central members to compensate for wear on the material engaging ends of the outer members, means to move the upper punch from a loading position, above the die to a forming position in the die, means to move the lower punch from a loading position in the die, where the die including the outwardly tapered upper portion thereof above the lower punch and annular pocket of the lower punch are filled with the powdered material, and a forming position to lower the material into the die and causing the extra amount of the material to till the annular pocket of the upper punch when moved into its forming position, whereby the inner and outer members of the punches in their forming positions will form an article, of the material, with annular flanges formed of the portions of the material in the annular pockets of the punches.

References Cited in the tile of this patent UNITED STATES PATENTS 1,232,297 Hambuechen an July 3, 1917 1,641,553 Schemmel Sept. 6, 1927 1,908,774 Maier May 16, 1933 2,325,687 Kux Aug. 3, 1943 2,437,127 Richardson Mar. 2, 1948 FOREIGN PATENTS 12,946 Great Britain of 1884 18,448 Great Britain Q Aug. 27, 1903 

